1. Field of the Invention
The present invention relates to a microscope technology, and particularly to a microscope used for the phase-contrast observation and the fluorescence observation.
2. Description of the Related Art
In the field of microscopy, the phase-contrast observation is an observation method that has been in use for a long time. When the phase-contrast observation method is used, the distribution of the refractive indices of a phase object (substantially transparent; only refractive indices are different) such as a specimen from a living-body can be visualized. Therefore, phase-contrast observation has been an appreciated method in biological disciplines.
In contrast, in the field of microscopy, fluorescence observation is an observation method that has grown importance in relatively recent years. In fluorescence observation, a fluorescent material is introduced into a specimen prior to observation and excitation light is irradiated onto the specimen. Then, by detecting fluorescent light generated from the specimen, the specimen is observed. In this case, by localizing the fluorescent material in a specific region in the specimen, fluorescence can be emitted from a portion of the specimen that is desired to be seen. Alternately, by relating the fluorescent material to a specific protein in the specimen, information directly related to an organic activity can be obtained.
In fluorescence observation, however, the shape of a specimen cannot be observed well. Therefore, it is necessary to examine which region in the specimen is emitting fluorescence using another observation technique. In this case, a differential interference contrast observation and a phase-contrast observation are generally used.
With a differential interference contrast microscope, however, a specimen is observed using polarized light. In differential interference contrast observation, therefore, the use of plastic-bottom dishes, which are often used for the observation of specimens from a living body, is limited.
In phase-contrast observation, by contrast, a microscope needs to comprise a special objective and a special condenser lens for the phase-contrast observation; and further it needs to comprise a ring slit placed at its pupil position. Therefore, when the phase-contrast observation and the fluorescence observation are combined to perform an observation, the overall number of parts used in the microscope is high. Since different parts are needed for the respective observations, the work of changing parts needs to be done. This hinders the ability to simultaneously perform phase-contrast observation and fluorescence observation.